These details are very similar for all models of Zebra including GC420, QLn220

Printer Properties

The Printer Needs to configured properly to print from the PDF files rendered from WeedTraQR.
These settings are specific to your printer, and the type of labels you purchase.
You will need to configure your Zebra properly for alignment, density and necessary stock details.

After changing any settings you may need to restart any running Browsers or PDF Viewers so they get the new settings.

Printer Settings Tab

Check Always use drivers settings

Printer Stocks Tab

Configure Stocks for each of the label sizes you have.
When printing from Firefox or Chrome select that stock (Properties) which matches the format in WeedTraQR.
It should remember it every time.